文摘
The Cauchy problem of the compressible Euler equations with damping in multi-dimensions is considered when the initial perturbation in H 3-norm is small. First, by using two new energy functionals together with Green’s function and iteration method, we improve the L 2-decay rate in Tan and Wang (2013) and Tan and Wu (2012) when \(\left\| {(\rho _0 - \bar \rho ,m)} \right\|_{\dot B_{1,\infty }^{ - s} \times \dot B_{1,\infty }^{ - s + 1} } \) with s ?[0, 2] is bounded. In particular, it holds that the density converges to its equilibrium state at the rate \((1 + t)^{ - \tfrac{3} {4} - \tfrac{s} {2}} \) in L 2-norm and the momentum decays at the rate \((1 + t)^{ - \tfrac{5} {4} - \tfrac{s} {2}} \) in L 2-norm. Moreover, under a weaker and more general condition on the initial data, we show that the density and the momentum have different pointwise estimates in dimension d with d ?3 on both space variable x and time variable t as \(\left| {D_x^\alpha (\rho - \bar \rho )} \right| \leqslant C(1 + t)^{ - \tfrac{d} {2} - \tfrac{{\left| \alpha \right|}} {2}} (1 + \tfrac{{\left| x \right|^2 }} {{1 + t}})^{ - r} \) with \(r > \tfrac{d} {2} \) and \(\left| {D_x^\alpha m} \right| \leqslant C(1 + t)^{ - \tfrac{d} {2} - \tfrac{{\left| \alpha \right| + 1}} {2}} (1 + \tfrac{{\left| x \right|^2 }} {{1 + t}})^{ - \tfrac{d} {2}} \) by a more elaborate analysis on the Green’s function. These results improve those in Wang and Yang (2001), where the density and the velocity (the momentum) have the same pointwise estimates.